P0325: The knock sensor circuit on Bank 1 has a fault
Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)
There is a fault in the knock sensor circuit (bank 1), so the engine cuts timing as a precaution. Get it checked within a week and use the fuel grade your manual asks for. If you hear knocking, stop driving.
Stop driving and get help if
- The check engine light is flashing
- The temperature gauge runs high, or you see steam (overheating)
- The car loses power, hesitates badly or stalls
- You smell burning or see smoke
- A brake warning light comes on, or the brakes feel different
Pull over as soon as you can, turn the engine off, and call a tow or roadside help.
What it means
The knock sensor listens for the high-frequency vibration signature of detonation, which is uncontrolled combustion in the cylinder. When it hears knock, it signals the PCM to retard ignition timing until the knock stops. P0325 means the PCM detected an open, short, or out-of-range resistance in the knock sensor circuit, not that knock is currently happening. With the sensor offline, the computer cannot detect actual knock, so it defaults to a safe, conservative timing map. The engine will run more conservatively, but you are also driving without the protection that sensor provides.
Common causes
- Failed knock sensorThe piezoelectric element inside the sensor degrades over time. Most common on engines past 100,000 miles.
- Damaged or corroded knock sensor wiring harnessThe harness runs near the block and can chafe, especially after engine work disturbs the routing.
- Loose knock sensor mountingThe sensor must be torqued to spec. A loose sensor outputs incorrect signals or no signal at all.
- Failed PCM input channel for the knock sensorRare. Rule out the sensor and wiring first.
What the fix could involve
From the cheaper fix to the bigger one. Prices depend on your car, your area and the shop, so ask for a written quote that names the part and the labor before you approve it.
- Wiring or harness repair
- Knock sensor replacement
- Knock sensor under intake manifold (some V6/V8 engines)
Symptoms
- Check engine light on, steady
- Noticeable reduction in power and throttle response
- Worse fuel economy
- Usually no audible knock (but the sensor cannot confirm it either way)
What to do next
The knock sensor on some engines, particularly GM V6 and V8 engines, is located under the intake manifold. The replacement cost is mostly labor for the manifold pull. On other engines it is accessible in minutes. Before buying a sensor, inspect the wiring and connector at the sensor. A broken harness clip or chafed wire is a cheaper fix. Always torque the new sensor to spec: under-torqued sensors generate false signals.
Lewis shows live ignition timing advance so you can see how much timing the engine computer is running while the knock sensor fault is present. Get Lewis on the App Store or Google Play.
Related codes
FAQ
- Is it safe to drive with P0325?
- Get it checked within a week. With the knock sensor offline, the engine cannot detect or respond to detonation, so do not use lower-octane fuel than recommended, and avoid hard acceleration. If you hear knocking or pinging, stop driving.
- Will fixing P0325 restore my lost power?
- Yes. Once the sensor is working, the PCM removes the conservative timing retard and power returns to normal.
- Why is the knock sensor under the intake manifold on some engines?
- Centering the sensor on the block gives it the best sensitivity to vibration from all cylinders. Unfortunately that location is underneath the intake manifold on many V-type engines.
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